1. Field of the Invention
The present invention relates to a facsimile communication system and more particularly to the facsimile communication system to perform facsimile communications through a communication network including a packet communication network or a like which uses a communication protocol being different from that applied to a telephone network.
2. Description of the Related Art
A communication procedure for the facsimile device connected to a public telephone network is designated in ITU-T (International Telecommunication Union-Telecommunication Standardization Sector), Recommendation T.30. According to the recommended communication procedure, generally, after a call is made, predetermined control signals are exchanged in consecutive order and data such as picture data is sent and received. In the facsimile device, in order to check if communications are normally performed, whether a valid signal is received within a predetermined time after a signal for the facsimile communications is sent is monitored. If the valid signal is not received within the predetermined time, the signal previously sent is transmitted again. If the re-sending is repeated predetermined number of times and nevertheless the valid signal is not received, the facsimile communication system judges a communication failure to have occurred and stops the subsequent facsimile communications forcedly.
In recent years, as an Internet becomes rapidly widespread, a communication procedure to implement the facsimile communications which can be performed through the Internet is proposed. According to the proposed communication procedure, each of paired facsimile devices is connected through the telephone network to each of gateway devices. The gateway devices are connected to each other through a packet communication network constituting the Internet. In the packet communication network connecting both the gateway devices, mutual communications are performed in accordance with the communication procedures designated in the ITU-T, Recommendation T.38.
However, the conventional facsimile communication system as described above have the following problems to be solved. That is, in the conventional communication network, if a traffic amount increases due to increased amount of the packet, there is a risk of the local occurrence of big delays in communications. While the facsimile communications are performed, remarkable delays in communications between both the gateway devices develop. If such delays in communications develop between both the gateway devices, the delays in communications are transferred to the telephone network connecting the facsimile device to the gateway device. According to the communication procedures designated in the ITU-T Recommendation T.30 described above, if the communication delays exceeding a predetermined scale develop, a communication failure is judged to have occurred and the subsequent facsimile communications are forcedly stopped.